This is atop level project that focuses on understanding the organizational of functional loops at the tissue level and the consequence of applying neurotransmitters (i.e drugs) to the loop topology. However, we will not in this phase attempt to obtain molecular or cellular descriptions in this project. Rather the focus will be to compare the results from this project with projects 1-3 to understand the similarities and differences in how exogenously administered drugs reconfigure the organization of loops in networks between cells and within cells. Just as proteins and other signaling components form intracellular networks that regulate information flow, cells form networks to communicate with one another to function in a coordinated manner and regulate information flow. Indeed all tissues and organs can be appropriately considered as networks of communicating cells that allow for information propagation so as to achieve stability as well as unified functions. One of the central issues in network biology is the understanding of the scalability of organizational principles. The issues regarding scalability across domains are complex, and often do not lend themselves to direct analysis. However, due to the nature of the systems being studied and the expertise of the participating investigators, it is feasible to ask directly whether some of the organizational principles found in intracellular signaling networks can also be found in networks of cells. The experimental system and the methodologies are very different, of course, so at first glance the overall system at the two different scales may bear little resemblance to one another. However, it is possible to mathematically abstract the functional data that measures information propagation and examine the organization of the network at both levels. It is with this logic that we have chosen this system. In this network of neurons in the dorsal LGN of the mammalian thalamus, we will study the role of intrinsic, feedforward and feedback loops in determining the dynamics of information processing in the brain. Specifically, we will examine the effects of topology of the loops among LGN neurons on the amount and kind of visual information that the LGN transmits from the retina to the visual cortex.